1. Field
The present disclosure relates to acoustic materials, methods of manufacturing the same, and methods of manipulating sound waves using the same for purposes of noise control.
2. Description of Related Art
Conventional materials and methods for noise control are divided into two general categories: sound blocking and sound absorption. With regard to the first category, sound blocking involves the impedance or prevention of sound from entering or leaving a space (e.g., room). With regard to the second category, sound absorption involves the reduction of the sound bouncing around inside a space (e.g., room), thereby decreasing or eliminating echoes and reverberations within. Thus, with sound absorption, the source of the sound is in the same room with the listener (unlike the situation with sound blocking).
Conventional noise control methods rely heavily on passive “add-on” treatments, such as damping and absorptive materials. Passive control approaches are used because they are relatively inexpensive and easy to implement. However, their performance is not optimal and also limited to the mid and high frequency range. Conventional passive methods, such as adding mass, damping, or acoustic absorption, etc., not only impose a stiff weight penalty, they are also ineffective in improving the low-frequency sound transmission loss of structures.